Soluble oil and process of producing same



Patented Dec. 30, 1947 UNITED STATES PATENT om SOLUBLE OIL AND PROCESS OF PRODUCING SAME Philip L. Carter, Media, and Walter J. Coppock, Rldley Park, Pa., assignors to Sun Oil'Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Application March 15, 1948,

- 'Serial No. 479,264

1 '14 Claims.

This invention relates to lubricating compositions for metal working operations such as cutting, grinding, drawing, cold rollin and the like. Compositions prepared according to the invention likewise have utility as spray oils and rust proofing oils. By way of conventional designation in alkali metal naphthenate, for example sodium.

naphthenate. It is also known to use. as a naphthenic acid source material for the preparation of alkali metal soaps in mineral oil intended for soluble oil service, the naphthenic acid mixtures obtainable from petroleum.

In a particular embodiment, to which the present invention is especially applied with worthwhile efifectiveness, soluble oils are prepared by saponifying an oil-naphthenic acid mixture derived from certain petroleum crude sources as hereinafter more particularly described. The soap-oil mixture thus obtained is, upon adjustment to desired or necessary viscosity and soap June 3, 1930, to Arthur E. Pew,Jr. Petroleum naphthenic acids of the original crude are converted to the corresponding sodium salts upon the aforesaid caustic soda treatment prior to. lu-

bricating oil distillation; and these naphthenates' accumulate in the residuum or still bottoms. They may be reverted subsequently by acidification of the residuum, as with sulfuric acid, and the petroleum naphthenic acids eventually recovered in mineral oil dilution by distillation of the residuum. The acids thus obtained in the overhead fraction of such residuum distillation have molecular is disclosed and claimed in U. S. 1,761,153 issued 2 weights varying from about 220 to 440; and a boiling range within that oflubricating oil. As recovered they are associated with relatively heavy lubricating oil, in which the concentration oi naphthenic acids may, for example, vary from 20 to 70 per cent.

Such a. method for recovering naphthenic acids from petroleum residuum is included in the disclosure of U. S. 2,056,913, issued October 6, 1936, to Terrell et al. cludes a step of diluting the acidified residuum with light oil prior to distillation, but for the purposes of the present invention this step may be included or not as desired.

Further information concerning the type of naphthenic acids here under discussion in reference to a specific embodiment of the present invention may be found in the article entitled, "Naphthenic acids from Gulf Coast petroleum," by Harkness and Bruun, appearing at pp. 499-502, vol. 32, No. 4 (April 1940), Ind. & Eng. Chem.

The term "crude naphthenic acids" as used herein is intended to mean and to designate a mixture of lubricating oil and petroleum naphthenic acids derived as aforesaid with a variable,

and non-critical concentration of acids within in the range of 10 to 80 per cent.

A usual procedure in preparing soluble oils ing crude naphthenic acids as saponifiable ma'-' terial for conversion to the necessary emulsify ing agent is as follows: Crude naphthenic acids" obtained as herelnbeiore described are adjusted to a saponification value of about 20 to 30 mg. KOH/gram. This is efiected by the addition of light lubricating oil in the case of .crude naphthenic acids having asaponification value higher than the indicated range; and by the addition or blending in of high saponification value crude naphthenlc acids in the case of material having an initially low (1. e., below 20) sapo'nification value. The oil-naphthenic acid mixture of 20-30 v saponification value then is completely neutralized by treatment withsodium hydroxide in s'iii butyl carbitol. butyl cellosolve, isopropyl aicohol' or the like is added, particularly whenhigh grade soluble oils are being manufactured. The mutual solvent is used in proportions usually less than 1 per cent. a f

The soluble oil product thus prepared later is The specific procedure there indiluted to an appropriate degree for its intended service as, for example, in metal cutting operations, such aqueous dilution being effected under conditions including agitation that give rise to emulsion formation. This emulsification of the soluble oil usually is done at the point of service use. When the soluble oil is used in emulsified state, it is of course essential that the emulsion be very stable, 1. e. highly resistant. both in storage and in use, to oil separation. Emulsifled soluble oils which "brea clearly have little appeal to the trade and, accordingly, the emulsifyingproperties with particular reference to emulsion stability are highly important.

Soluble oils prepared as hereinbefore described, using saponified naphthenic acid material, often have satisfactory emulsifying properties. In many cases, however, difficulty has been experienced when using "crude naphthenic acids" from certain petroleum crudes. Investigation thus far has failed. to provide an answer to the problem of why "crude naphthenic acids from certain crudes are satisfactory while others are definitely inferior as source material for emulsifying agents in soluble oil compositions. The difficulty in question has arisen with different crudes from the same general source, i. e., different Gulf Coastal crudes, all naphthenic or asphaltic base in character, which may inone instance yield satisfactory crude naphthenic acids and in other instances yield unsatisfactory crude naphthenic acids. The crudes generally are the same as to most characteristics .and the naphthenic acids in all cases are of the same molecular weight range. Regardless of the explanation which eventually may be forthcoming, and which of course has no special bearing upon the solution of the problem provided by the present invention, the fact remains that both "good acids" and poor acids are encountered. These terms, good acids and poor acids, are colloquial but recognized in the trade; and are used merely to differentiate between more and less useful batches of "crude naphthenic acids in the sense of the capacity of such material for production of good or poor emulsifying agents as used in soluble oil manufacture.

It has now been discovered that the foregoing difliculty may be obviated and certain attendant other advantages realized by applying to crude naphthenic acids, prior to saponiflcation thereof, a novel conditioning treatment.

This treatment comprises sulfonating crude naphthenic acids" or a lubricating oil mixture containing such material and which is intended for soluble oil manufacture by saponification of the acidic components. The resulting soluble oil prepared by a method including the novel sulionation step of the present invention is characterized by marked improvement in emulsion stability, and also has enhanced utility in that such an improved soluble oil is free from rusting or corroding tendencies under the conditions of metal working service.

The aforesaid improvement in soluble oil quality obtains generally when sulfonation according to the invention is included in the manufacture of soluble oils from fcrude naphthenic acids, whether these be good acids" or poor acids." The invention has outstanding utility in the latter case in that it makes possible the use of a material otherwise an economic waste. In other words, such poor acids now may be used in the manufacture of soluble oils either per se or in admixture with good acids and excellent emulsifying properties are imparted to the resulting soluble oil.

In applying the present invention to the manufacture of soluble oil, the aforesaid preconditioning treatment is employed to produce a sulfonated naphthenic stock. This is accomplished by treatment of an unsulfonated stock, comprising a mixture of naphthenic acids and untreated lubricating oil with a sulfonating agent, as for instance, concentrated or fuming sulfuric acid and desirably at an elevated temperature. The sulfonating agent preferably is added in increments in a manner similar to the well known acid treatment of lubricating oils, the sludge formed after each incremental treatment being settled out, withdrawn and discarded. The treatment with increments of sulfonating agent is continued until the organic SO: content of the batch has reached the desired value, the organic SO: being taken as an index of the amount of sulfonation that has been effected. The thus prepared sulfonated stock then is blended with various ingredients and the blend is neutralized with alkali to form the finished emulsifying oil, as more fully described hereinafter.

In preparing a sulfonated stock, it has been found that material containing on the one hand a very small amount of naphthenic acids and on the other hand a very small amount of oil exhibits resistance to the desired sulfonation (i. e., the formation of sulfonic acids which remain in the oil-acid mixture as opposed to such sulfonic acids as may be lost as sludge). It has now been discovered that mixtures containing substantial amounts of both naphthenic acids and lubricating oil can bereadily sulfonated and, further, that there is an optimum naphthenic acid concentration for maximum sulfonation. This is illustrated by the following data which show the organic SO: contents of blends of a naphthenic base lubricating oil having a S, U. viscosity of about 100 seconds at 100 F, and naphthenic acids after treatment at about 200 F. with oleum (20 per cent fuming sulfuric acid) in increments of 20 lbs. oleum per bbl. of stock:

Per Cent Organic S0:

Per Cent Sap. Value of Stock, g ggggg After treat- After treatmg KOH/g Stok mleghigith mgbtlglth Oieum/bbl Oicum/bbl.

g Noie (6.2g 0. 94 17 10 1111 "'if'zf" 32 18 1. 45 2. 04 B0 34 1. 56 2. 43 45 1. 35 2. 09 136 77 1. 04 1. 12 174 98 0.13

The results are given for two series of treatments in which the total amount of sulfonating agent was and 200 lbs/bbl. of untreated stock, respectively. Maximum sulfonation is attained when the saponification value of the original blend is approximately 60 mg. KOH/g. corresponding to about 34 per cent naphthenic acids.

The degree of sulfonation decreases if the concentration of naphthenic acids is either substantially higher or lower than about this value.

The exact mechanism of the sulfonation reaction is not understood, nor is the precise role of the naphthenic acids in effecting increased sulfonation known. There is some evidence that the naphthenic acids act as a promoter or accelerator for the sulfonation of the neutral oil present in the mixture with probably some sulfonation of the naphthentic acids. It has been found that a decrease in the naphthenic (or weak acid) acidity invariably accompanies sulionation and that the decrease is related to the severity of the sulfonating conditions, but whether this is due to actual sulfonation of the naphthenic acids or to some other cause is not known. Thus far, the complexity of the reaction has obscured the role of the naphthenic acids to such an extent that any theory which might be advanced would serve no useful purpose.

As the sulfonating agent, use has been made of sulfuric acid of strengths from 66 B. (93% H2804) up to 60% fuming acid, as well as sulfuric anhydride and chlorosulfonic acid. ,Sulfuric acid is preferred due to its low cost and ease of handling. It has been found that the amount of sulfonation tends to increase as the strength of the sulfuric acid is increased up to a concentration of 20 per cent fuming acid but that any increase in acid strength above this concentration results in substantially no additional -sulfonation. A concentration of 98% H2804 is pre-- ferred, since this. strength gives a satisfactory amount of sulfonation without the difliculties of handling that fuming acid would present. following data show the degree of sulfonation obtained and the amount of sludge formed when various amounts of 93% H2802, 98% H2804 and 20 per cent fuming acid are used in increments of 20 lbs./bbl. at a treating temperature of about 200 F.

The tabulated values for per cent organic 80: show that 98 per cent H2804 is substantially more eifectivethan 93 per cent H2804 but that oleum is only slightly more effective than 98 per cent H2804. There is little difference in the amount of sludge formed between strengths from 93 per cent H2804 up to at least 20 per cent fuming acid.

It further has been found that there is an optimum treating temperature for obtaining maximum suifonation and that the use of treating temperatures either higher or lower than the optimum will result in a lower degree of sulfonation. The optimum temperature may vary somewhat but usually lies within the range of 175 F. to 225 F. This is illustrated by the following data on a stock (having a saponification value of 20) treated at various temperatures with a total of 60 lbs. of sulfonating agent/bbl. in increments of 20 lbs./bbl.

Per Cent 0rgnnic $03 in product Treating 'Icmp., F.

The

For this stock a substantially maximum degree of sulionation was reached at about 175 F. when either 98 per cent H2804 or oleum was used. For certain other stocks a'temperature as high as 225 F. has been required for maximum sulfonation, although, in these cases, treatment at 1'75- 200 F. resulted in a degree of sulfonation approaching the maximum. Increasing the treating temperature above about 225 F. usually causes a decrease in the amount of sulfonation- In addition to its relationship to the amount of sulfonation, the treating temperature also affects the corrosion or rust inhibiting characteristics of the product. With sulfuric acid as the sulfonating agent, treating temperatures below about 175 F. tend to give a product having inferior inhibiting characteristics. Higher temperatures, for instance-200 F. or higher, result in a product free from rusting or corroding tendencies under metal working service conditions. In commercial practice, a treating temperature of about 200 F. is preferred since this easily may be attained, gives substantially th maximum degree of sulfonation and results in a suitable pr0duct. However, temperatures of about 150-250 F. maybe taken as a generally useful range for effecting the sulfonation by means of sulfuric acid.

It also. has been found that there is an optimum amount of sulfonating agent for maximum sulfonation, This optimum amount varies considerably with the stock being treated and the particular treating conditions. In one set of treats in which "crude naphthenic acids and a preferred light lubricating oil were blended in various proportions to give stocks having saponiflcation values of 17, 32, and 136 and these stocks were treated with various amounts" of oleum in increments of 100 lbs./bbi., the following Organic contents were obtained:

Per Cent Organic 80; in product Total amount oi Oleum used lbs'lbbl' Sap. Sap. Sap. Sup.

' valuevalue-32 valuo=il0 vnlue==i36 1.17 0.45 1.56 1.04 1. 26 2. 04 2. M l. 12' 0. 99 l. 57 1. 0.87

In each case maximum sulionation was attained with 200 lbs. of oleum per bbl, and an increase in the proportion of oleum to 300 lbs./bbl. caused a decrease in the amount of sulfonation. Addithe amount usually employed varies from 20 to 80 lbs. per bbl. of untreatedstock, depending on the particular procedure used in subsequently compounding the soluble oil.

The size of the increments of sulfonating agent is'another factor affecting the degree of sulfonation attained. In general, the smaller the size of increments, the greater is the amount of sul fonation for a given total amount of sulfonating agent. Thus, it has been found that increments 7s of 50 lba/bbl, are substantially more eifective asses-to than 100 lbs./bbl. and that increments of 20 lbs./bbl. are still more efiective. Further decreases in size below 20 lbs/bbl. eflfect substantially no additional improvement and only result in the multiplication of the number of treating steps. Consequently, increments of approximately 20 lbs/bbl. are preferred.

The viscosity of the untreated lubricating oil blended with the naphthenic acids to produce the untreated stock has a small but definite effect on the amount of sulfonation that will be obtained. In general, the degree of sulfonation will increase with increasing viscosity of the oil used. However, since the effect is small and since lower viscosity oils are usually less expensive, it usually is preferable to use a light lubricatin oil, for instance, one having a S. U. viscosity of 100 seconds at 100 F. and obtained from crudes of the Gulf Coastal type. I

The sulfonated naphthenic acids prepared as described hereinabove may be used either with or without untreated naphthenic acids to prepare a soluble oil having the characteristics desired. For any particular case there are rather definite minimum proportions of both naphthenic and sulfonic constituents required in the soluble oil to ensure attainment of the desired quality. Experience has shown that the soluble oil prepared according to the present invention should contain naphthenates equivalent to a saponification value of not less than about 16-18 and, when sulfuric acid or oleum has been used as the sulfonating agent, usually'should have an organic SO: content not less than 0.45-0.60 'per cent corresponding to a strong acid saponification value of about 3-4. When sulfur trioxide has been used for efiecting sulfonation, a lower organic SO: content usually will prove to be satisfactory. A soluble oil having the above specified concentrations of naphthenate and sulfonate constituents will have adequate emulsion stability and, when used in aqueous dilution for metal working operations, will inhibit or prevent rusting of the metal. In contrast to such specifications,

when the novel preconditioning treatment as accordance with the present invention may be.

varied considerably to utilize the particular stock of "crude naphthenic acids available. Usually stocks of both "good naphthenic acids and poor naphthenic acids will be available; and in such case the preferred procedure comprises blending sulfonated stock prepared from the "poor naphthenic acids by the procedure hereinabove disclosed, untreated naphthenic acids of good quality and an untreated distillate lubricating oil having a S. U. viscosity of 100 seconds at 100 F. in such proportions that the" blend has a naphthenic saponification value of about 16-18 and an organic SO: content of about 0.45-0.60 per cent. This blend then is neutralized with 50 B. caustic soda, a slight excess of caustic soda 8 being used. A small amount (usually less than 1 per cent) of a mutual solvent for oil and water is addedand the water content of the blend is adjusted to approximately 2 per cent to yield a finished soluble oil of excellent quality.

The viscosity of the lubricating oil used for compounding the soluble oil is of relatively minor importance. Preferably, a light lubricating oil is used in order that the viscosity of the resulting soluble oil will be relatively low; however, heavier oils may be used if desired.

Larger proportions of both the sulfonated stock and untreated naphthenic acids than specified hereinabove may be used in compounding the soluble oil if desired. However, such larger proportions eifect little if any improvement in the soluble oil but merely result in an increased consumption of these valuable constituents.

In testing soluble oils for emulsion stability, 10 parts of the oil are poured into 90 parts of water at a temperature of 45 F. while the water is being mildly agitated. The thus formed emulsion, after prolonged standing, should show substantially no oil film on its surface and no more than a. slight amount of creamy cuff. Actual service tests are the best means of determining the noncorrosiveness and rust-inhibiting characteristics of the soluble oil.

The following examples, in which parts are b weight, serve to illustrate how the present invention may be carried out in practice:

Example 1 Twenty-five parts of "crude naphthenic acids" of the poor quality type obtained by the Terrell et al. process and having a saponification value of 83 were blended with 75 parts of a light lubricating oil obtained from a mixture of Gulf Coastalcrudes and having a viscosity of 100 seconds at 100 F., thereby to form a stock having a saponification value of 21. The stock was heated to 200 F. and treated at this temperature with three successive increments of 98 per cent sulfuric acid, each increment amounting to 20 lbs.

per bbl. of the blend. After each incremental treatment the sludge formed was separated and withdrawn. Eighty-nine parts of the sulfonated stock, having a naphthenic saponification value of 18 and an organic S03 content of 1.24 per cent, thereby were obtained. These were blended with crude naphthenic acids of good quality and a light lubricating oil of the type described above in the following proportions:

. Parts sulfonated stock 89 Naphthenic acids (128 sap. value) 11 /2 Lubricating oil 78 The resulting blend, having a naphthenic saponification value of 17 and an organic S'Oa content of 0.60 per cent, was saponified by mixing with 2.52 parts of 50 B. caustic soda. A finished soluble oil was obtained by adjusting the water content to 1.9 per cent and adding 0.6 per cent of butyl cellosolve. This soluble oil passed the emulsion stability test and, in actual service, was shown to be non-corrosive and to inhibit rusting.

Example 2 Poor quality naphthenic acids and light lubricating oil, both similar to the materials used in Example 1, were blended to form a stock having a saponification value of 22. This stock was cent sulfuric acid, each increment amounting to 20 lbs./bbl. of untreated stock. After each incremental treatment, the sludge was withdrawn and discarded. The thus treated stock, having a naphthenic saponiflcation value of 20 and an organic SO: content of 0.82 per cent, was saponifled with 50 B. caustic soda. The water content was adjusted to approximately 2 per cent,

and 0.6 per cent of butyl cellosolve was added.

The thus formed soluble oil passed the emulsion stability test satisfactorily and had the desired rust inhibiting and non-corrosive characteristics.

We claim: a

1. The process of making a soluble oil which comprises treating a mixture of naphthenic acids and untreated lubricating oil with a sulfonating agent under sulfonating conditions to form a sulfonated stock and neutralizing the thus formed stock with an alkali metal hydroxide thereby to form the soluble oil.

2. The process of making a soluble oil whichcomprises treating a mixture of naphthenic acids and untreated lubricating oil having a saponiflcation value not substantially less than 18 with sulfuric acid having a strength of not less than 93 per cent H2504 and at a temperature within the range of 150 F. to 250 F. to produce a sulfonated stock, neutralizing the thus formed blend with alkali metal hydroxide, adjusting the water content of the neutralized blend to approximately 2 per cent and adding a minor amount of a mutual solvent to the resulting mixture thereby to form said soluble oil.

3. The method of producing from naphthenic acids and untreated lubricatingoil a relatively highly sulfonated stock which comprises treating a mixture of naphthenic acids and untreated lubricating oil containing not less than 5 per cent nor more than 90 per cent naphthenic acids with a sulfonating agent at an elevated temperature,

whereby the resulting degree of sulfonation is greatly in excess of that which would be obtained by treating each of the said starting materials which comprises treating a mixture of naphthenic acids and untreated lubricating oil containing not less than 5 per cent nor more than 90 per cent naphthenic acids with a sulfonating agent at an elevated temperature, whereby a sul-.

fonated stock is formed having a degree of sulfo nation greatly'in excess of that which'would be obtained by treating each of the said starting materials separately and blending together the separately treated materials, and neutralizing the thus formed stock with an alkali metal hydroxide thereby to produce the soluble oil.

5. In a method of preparing emulsiflable lubricating compositions which comprises forming a mixture of petroleum naphthenic acids and lubrieating oil, adjusting the saponification number of the mixture to provide, after saponification, an effective proportion of emulsifier and neutralizing with an alkali metal hydroxide to form a slightly alkaline composition, the improvement which comprises treating the said mixture of naphthenic acids and lubricating oil with a sulfonatlng agent under sulfonating conditions prior to the aforesaid neutralization.

6. In the process of making a soluble oil of the type'herein described, the step of preparing a sulfonated stock which comprises subjecting a w mixture of naphthenic acids and untreated lubrieating oil to treatment with sulfuric acid having a strength of not less than about 93 per cent H2804 and at a temperature within the range of 150 F. to 250 F., said mixture containing not less than 5 per cent nor more than 90 per cent naphthenic acids, whereby a sulfonated stock is,

formed having a degree of sulfonation greatly in excess of that which would be obtained by treating each of the said starting materials separately and blending together the separately treated materials.

7. In the known process of producing a soluble oil by saponifying the acidic constituents of a mixture of naphthenic acids and lubricating oil with alkali metal hydroxide, where the available naphthenic acids comprise those which, when subjected to the above process, produce a soluble oil having satisfactory emulsifying properties, the herein described improvement which permits utilization of a smaller proportion of naphthenic acids than otherwise would be permitted in producing a soluble oil having satisfactory emulsifying properties; said improvement comprising treating said mixture, prior to saponification, with sulfuric acid having a strength of not less than 93 per cent H2SO4 and at a temperature within the range of 150-250 F. to thereby produce a sulfonated stock which, when subjected to saponification, produces a soluble oil of satisfactory emulsifying properties.

8. In the known process of producing a soluble oil by saponifying the acidic constituents of a mixture of naphthenic acids and lubricating oil with alkali metal hydroxide, the herein described improvement which permits utilization of such a mixture which, when subjected to said known process, produces a soluble oil having unsatisfactory emulsifying properties; said improvement comprising treating said mixture, prior to saponification, with sulfuric acid having a strength of not less than 93 per cent H2804 and at a temperature within the range of 150-250" F. to thereby produce a sulfonated stock which, when subjected to saponification, produces a soluble oil of satisfactory emulsifying properties.

9. In the known process of producing a soluble oil by saponifying the acidic constituents of a mixture of naphthenic acids and lubricating oil with alkali metal hydroxide, where the available naphthenic acids comprise those which, when subjected to the above process, produce a 1 soluble oil having satisfactory emulsifying properties and also comprise those which, when subjectedto the above process, produce a soluble oil having unsatisfactory emulsifying properties, the herein. described improvement whereby both classes of naphthenic acids may be utilized to produce a soluble oil of satisfactory emulsifying properties; said improvement comprising treating a mixture of such inferior naphthenic acids assaeee and untreated lubricating oil having a saponification value not substantially less than 18 with sulfuric acid having a strength 0! not less than 93 per cent H2504 and at a temperature within the range of 150 F. to 250 F. to produce a sulfonated stock and neutralizing the sulfcnated stock with alkali metal hydroxide.

12. The process of making a soluble oil which comprises treating a mixture of naphthenic acids and untreated lubricating oil containing 10-80 per cent naphthenic acids with a sulfonating agent and at a temperature within the range of 150 F. to 250 F. to produce a sulfonated stock and neutralizing the sulfonated stock with alkali metal hydroxide.

13. Method according to claim 3 wherein the said mixture of naphthenic acids and untreated lubricating oil contains 10-80 per cent naph thenic acids.

14. A- method of producing from a. mixture of naphthenic acids and lubricating oil a relatively g5 highly sulfonated stock which comprises subiecting such mixture containing not less than 5 per cent nor more than 90 per cent naphthenic acids to the action of a sulionating agent under suli'onating conditions, and correlating the concentration of naphthenic acids in said mixture with regulated sulfonating conditions including temperature, strength of sulfonating agent and quantity thereof to obtain a predetermined de-- gree of sulfonation, whereby the resulting degree of sulfonation is greatly in excess of that which would be obtained by treating each of the said starting materials separately and blending togather the separately treated materials.

PHILIP L. CARTER. WALTER J. COPPOCK.

REFEREIGCES CITED The following references are of record the file of-this patent:

UNITED STATES PATENTS Carlson Dec. 9, 1941 

